Cutting music costs for iPhone

[marscaleb]

I'm thinking that with all the high-res textures going into a UDK iphone game, we'd want to cut some corners where we can to reduce file size and memory. And as I was thinking about this, background music could be a big one.

I can't imagine wanting to cram in several minutes of quality audio to serve as background music, so I'm wondering what common practices I could follow to reduce that cost.

Does the engine still have access to some legacy music systems that could be used, and if so how would I go about creating music for such a system?
Could I have the game play midi files, perhaps?

(Or am I mistaken about how much the system can handle?)

[raziel2001au]

Well, music, more specifically, an MP3, is actually quite cheap on the iPhone, for two reasons:
1) Background music (that is an MP3), is streamed as it plays, it is not completely loaded into memory like a texture is.
2) The iPhone has a hardware decoder chip that essentially lets you decode and play one MP3 for free without the CPU having to do any work.

So in other words, you would save neither CPU power nor memory by not using an MP3 for background music. On the other hand, if you chose to use another format for music, this would have to be synthesized on the CPU itself, so you would incur a processing cost. In other words, MP3 is the cheapest option you have, just don't throw a 320kbps MP3 at it since at that point it would strain memory bandwidth which may affect the speed of your game, stick to 128kbps or even consider going lower if you can.

Just read the documentation on sound so you know how to start an MP3 on the iPhone the proper way (so it definitely uses the iPhone's hardware).


Raz.

[marscaleb]

Hey thanks, that's good to know!